The present invention relates generally to wind driven power generation plants and, more particularly, to an apparatus, method and system for directing wind into blades of a wind turbine to increase efficiency and power output.
The conversion of natural energy, e.g., solar energy, wind energy, ocean tidal and wave energy, into electrical energy is well known. Using natural energy sources has become more desirable in recent years because of concerns about the effects of fossil fuels on the environment and also because of the increasing cost of fossil fuels. Further, it is widely recognized that fossil fuels are in limited supply, thus further emphasizing the need to exploit natural energy sources.
The most common apparatus for converting wind energy into useful power is the windmill, which typically includes a plurality of blades directly exposed to the wind and interconnected to rotate about a common horizontal axis. In traditional windmills, the rotational axis is permanently aligned with the prevailing wind direction. Accordingly, efficiency suffers when the wind varies from the prevailing direction.
More advanced windmills have axes that can be moved, either by servomotors or by direct reaction to the wind, into alignment with the wind. These modern windmills exhibit greater flexibility than traditional designs, but they require expensive support bearings and still suffer from important deficiencies that are inherent in windmills. For example, an electric generator directly coupled to the axis of a conventional windmill is exposed to outdoor elements and, therefore, is susceptible to a high rate of corrosion. In addition, access to these high-mounted generators for maintenance purposes is difficult. Furthermore, the large, rotating blades of conventional windmills pose a significant safety hazard so that windmills must be located in areas of low population density, often on remote windmill farms.
Although windmills are a well-known means for harnessing wind energy, windmills suffer from several inherent disadvantages. Tall towers must typically be constructed to accommodate large-diameter rotors and to position them high enough in the air stream to avoid the undesirable effects of air turbulence caused by obstructions at ground level. Further, the major mechanical components, i.e., the generator and associated mechanical linkage to the turbine, as well as the turbine controls and positioning apparatus, are typically located atop the tower as well, thus making maintenance difficult and expensive. Additionally, windmills only effectively extract energy from a circular cross section of an air stream, thereby substantially limiting their capability of extracting power from the wind stream.
The necessary size of economically feasible wind driven power plants for the generation of electric power introduces technical problems that require qualitatively new solutions. In particular, it is not possible to build plants that are competitive with other power generating systems by merely scaling up the small wind generation systems that are known in the art. Construction means suitable for a small wind generator would require massive support structures if applied to a very large windmill so that the capital investment in such a windmill would be prohibitive.
Modern windmills require wind speeds of 9-12 m/s (meters/sec.) to generate useful levels of electrical energy. Generated Electrical Power is directly proportional to the cube of the wind velocity. (P=kV3). Hereinafter, windmills will be referred to as wind turbines. In the United States, only the Mt. Washington and Cold Bay, Ak. areas offer this intensity of average wind speed. Some isolated hilltops and canyons also offer potential for this level of wind speed; some of these sites are presently producing electricity at 10""s of MW power levels.
Many coastal areas in the United States have wind speeds averaging 6-7 m/s and these winds come from the same direction practically year around. For example, the South Texas Coastal Area, from Brownsville to Galveston, has 6-8 m/s wind speeds from the Southeast (approximately 150 degrees) 12 months a year.
Assume a wind turbine provides 1 MW (1 million watts) at a wind speed of 12 m/s. Some simple arithmetic tells us that it will generate approximately 579 kW at a wind speed of 10 m/s, and 296 kW at a wind speed of 8 m/s. In other words, a 50% increase in wind speed provided 4 times the output power.
Placing wind turbines adjacent natural hilltops and canyons or valleys between hilltops may improve performance because of airfoil and Venturi effects. Unfortunately, very few of these natural areas provide the smooth surfaces for laminar airflow and the ideal shapes to maximize wind speed, and minimize turbulence and wind sheer. Often, the valley direction is contrary to the prevailing wind direction. In other locations, such as the Texas coastline, for example, no hills or valleys are available to enhance or direct the wind.
Referring now to the drawings and more particularly to FIG. 1, a wind turbine 10 according to the prior art is depicted. The wind turbine 10 has a rotor 11 that converts wind 12 into electrical power. The rotor is attached to the wind turbine 10 through a hub 13, which is situated at an elevation above the ground known as the hub height 14. The hub height 14 is critical to the design of the wind turbine 10 because it determines the clearance between the rotor 11 and the ground. The hub height 14 also affects the exposure of the rotor 11 to the wind 12.
As wind 12 passes across the rotor 11, the wind 12 causes the aerodynamic shape of the rotor 11 to rotate the hub 13, which in turn drives an electric generator. Total power generation from the wind turbine 10 depends in part on the speed, direction and air density of the wind 12 that impacts the rotor 11. A rotor diameter 18 determines how much wind 12 the wind turbine 10 captures and converts to electricity. For optimum power generation, the wind 12 will blow directly into the rotor 11 at a relatively high, constant velocity. Consequently, turbulence in the wind 12 may adversely affect power generation from the wind turbine 10 because turbulent wind 12 is not efficiently turning the rotor 11.
It would, therefore, be desirable to have an improved wind power generation apparatus that does not require an extraordinary amount of wind in any particular direction. Additionally, there is a need for an improved wind power generation apparatus that does not require a location in any particular geographic area having particular geological features. Also, there is a need for an improved wind power generation system that is less susceptible to inefficiencies caused by inherent variations in the wind.
A wind power generation apparatus of the present invention includes a wind turbine having a rotor diameter and a hub height. An artificial mound adjacent to the wind turbine has a length, a width and a height. The artificial mound is positioned to enhance the performance of the wind turbine by focusing wind on the turbine rotor. The dimensions of the artificial mound are determined according to the characteristics of the wind turbine.
In one embodiment, a wind power generation apparatus includes a wind turbine having a rotor diameter and a mound adjacent to the wind turbine. The mound has a height from 0.1 times to 3 times the rotor diameter. The wind turbine is positioned with respect to the mound to enhance the performance of the turbine.
In yet another embodiment, a method for increasing the performance of a wind turbine includes the steps of locating an artificial mound to direct wind to a rotor on the wind turbine and building the artificial mound to a height that focuses the wind on the rotor of the wind turbine.
In another embodiment, a method for increasing the performance of a wind turbine having a rotor includes the steps of locating a mound having a height of between about 0.1 times and 3 times the rotor diameter of the wind turbine to direct wind to the rotor and positioning the wind turbine to maximize the wind on the rotor of the wind turbine.
In yet another embodiment, a system for increasing the performance of a wind turbine includes a wind turbine and a mound adjacent to the wind turbine to direct wind into a rotor of the wind turbine. The height of the artificial mound is between about 0.1 times to 2 times the rotor diameter.